I distinctly remember when I first started watching cricket back in the 70s, the one-day version of the game was starting to make its impact felt, and grave foreboding was expressed back then of its likely impact on the longer version.

Back then, if you saw 280 runs scored in a day's test cricket, that was a run-feast; 240-250 runs probably more typical.

Now, 400 runs (in a day's play) is closer to the norm.

The game is played at a faster pace and it's over more quickly.

More than that, to play adventurous shots entails greater risk, and the more risk you take, the more likely you are to come unstuck.

That is precisely what we see in the modern era; the game played at break-neck speed, batsmen giving away wickets cheaply and matches over (comparatively) in a trice.

Geoff Boycott predicted that, soon, we will have 4-day tests.

Wouldn't surprise me in the least if he is right ....

ETA: The other big difference is that, these days, international cricketers don't play domestic cricket (much).

Back in the 70s, test cricketers would play county cricket (or, in Australia, Sheffield-Shield cricket) in between their test commitments. It was, perhaps, a greater strain on the players, but at least they were playing regularly, which is key to maintaining form.

These days, players contracted to play for the national team just don't take part in the domestic game, and curtailment of playing time (I think!) results in a lowering of standards ....